Answer:
Although the LED's cannot be turned off permanently, it is possible to have them extinguish after 20secs of no interaction with the remote, loudspeaker touchpad and Hub buttons, but if you do use the remote or Hub buttons, the LED's will illuminate until another 20secs of no interaction passes before extinguishing again.
To make this change, open the Q Active app, from the list of discovered Q Active systems, choose the one you want to alter by tapping on the corresponding settings cog wheel. On the settings page, find the scrolling option 'Hub LED switch off after 20s', tap the ON toggle to turn this function on and off.
Once set, the setting is stored and will not be altered until changed within the Q Active app or a reset is performed to the system.
Note: This only effects the Q Active Hub, the loudspeaker LED indicators remain illuminated as normal.